Manual transmission oil composition having enhanced fuel efficiency and low viscosity

ABSTRACT

Disclosed is a manual transmission oil composition which include: (A) a polyalphaolefin (PAO) synthetic base oil in an amount of about 75 to 85 wt %; (B) an ester-based viscosity modifier in an amount of about 3 to 10 wt %; and (C) an additive in an amount of about 8 to 15 wt % which includes one or more of an anti-wear agent, a detergent dispersant, a friction modifier, an extreme pressure additive, and an anti-oxidant, based on the total weight of the manual transmission oil composition. Accordingly, the manual transmission oil composition may have a low viscosity as compared to conventional manual transmission oils, and may provide improvements in endurance of a transmission, reduction in a Rattle noise, and further improvement in fuel efficiency of vehicles by about 1 to 2%.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims under 35 U.S.C. §119(a) the benefit of Korean Patent Application No. 10-2014-0070362 filed on Jun. 10, 2014, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a manual transmission oil composition having improved fuel efficiency and a reduced viscosity. The manual transmission oil composition includes an ester-based viscosity modifier as a viscosity modifier which is added in a predetermined amount to a polyalphaolefin (PAO) synthetic base oil thereby reducing a viscosity difference in various ranges of temperatures. Accordingly, the endurance of a transmission may be improved even though a viscosity of the composition is reduced, and fuel efficiency and low temperature gear-shifting performance of vehicles may be improved.

BACKGROUND

Generally, a transmission is a device installed between a clutch and a thrust shaft or between the clutch and a final reduction gear to change turning force and a speed. Accordingly, power of an engine may be adjusted for a driving state of vehicles and thus the turning force and the speed may be transferred to a driving wheel. For example, a manual transmission changes a turning speed and turning force transferred from the engine through gear shifting according to a clutch operation and a driving condition which may be required to curb power, and transfers the turning speed and turning force to the driving wheel, and thus, a speed and torque required by a driver may be obtained.

In the related arts, the manual transmission for a vehicle has a synchronizer gear-shifting apparatus so as to smoothly perform a gear-shifting operation of the driver. The synchronizer gear-shifting apparatus may be an apparatus adjusting speeds of a clutch gear and a single gear during gear-shifting thereby providing a smooth gear-shifting operation. The synchronizer gear-shifting apparatus may be combined with a sleeve forming gearing while speed synchronization of the clutch gear and the single gear may be performed due to a contact of a synchromesh and an inclined surface of the single gear. When the oil viscosity is substantially increased, synchronization due to friction during the contact may be disturbed and the ability to sense gear-shifting may be reduced, particularly at an ambient air temperature of about −20 to −50° C. or less, thereby causing failure of gear-shifting.

In related arts, a method of reducing a viscosity of an oil at low temperatures has been developed. However, when the viscosity at the low temperature is reduced, the viscosity at high temperatures may be reduced accordingly, and thus this manual transmission oil may aggravate endurance of a transmission and a Rattle noise may be worsened.

Therefore, there is an unmet need for development of a manual transmission oil composition which may have the reduce viscosity and simultaneously improved endurance of the transmission, fuel efficiency, and low temperature gear-shifting performance.

The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.

SUMMARY OF THE INVENTION

The present invention provides technical solutions to above-described technical difficulties in the related art.

For example, when an ester-based viscosity modifier as a viscosity modifier is added in a predetermined amount into a polyalphaolefin (PAO) synthetic base oil, or when polyalkyl methacrylate is further added, a viscosity difference in various range of temperatures may be reduced, endurance of a transmission may be improved although a total viscosity is reduced. Further, fuel efficiency and low temperature gear-shifting performance of vehicles may be improved.

As such, a manual transmission oil composition may be obtained from the composition. The manual transmission oil composition may have an average kinematic viscosity of about 5 to 6 cSt at a temperature of about 100° C., an average kinematic viscosity of about 24 to 30 cSt at a temperature of about 40° C., and a low viscosity of an average absolute viscosity of about 5,000 to 10,000 cP at a temperature of about −40° C., thereby improving endurance of a transmission and enhancing fuel efficiency of vehicles by about 1 to 2%.

In one aspect, the present invention provides a manual transmission oil composition. The manual transmission oil composition may include: a polyalphaolefin (PAO) synthetic base oil in an amount of about 75 to 85 wt %; an ester-based viscosity modifier in an amount of about 3 to 10 wt %; and an additive in an amount of about 8 to 15 wt % including one or more selected from an anti-wear agent, a detergent dispersant, a friction modifier, an extreme pressure additive, and an anti-oxidant, based on the total weight of the manual transmission oil composition. Moreover, the manual transmission oil composition may further include polyalkyl methacrylate in an amount of about 3 to 5 wt % as the viscosity modifier based on the total weight of the manual transmission oil composition.

It is also understood that weight percents of the components as disclosed herein are based on total weight of the composition, unless otherwise indicated.

The present invention also provides the manual transmission oil composition that consist essentially of, or consist of the disclosed contents. For example, a composition is provided that consists essentially of, or consists of: a polyalphaolefin (PAO) synthetic base oil in an amount of about 75 to 85 wt %; an ester-based viscosity modifier in an amount of about 3 to 10 wt %; and an additive in an amount of about 8 to 15 wt % including one or more selected from an anti-wear agent, a detergent dispersant, a friction modifier, an extreme pressure additive, and an anti-oxidant. Further, a composition is provided that consists essentially of, or consists of, consists essentially of: a polyalphaolefin (PAO) synthetic base oil in an amount of about 75 to 85 wt %; an ester-based viscosity modifier in an amount of about 3 to 10 wt %; an additive in an amount of about 8 to 15 wt % including one or more selected from an anti-wear agent, a detergent dispersant, a friction modifier, an extreme pressure additive, and an anti-oxidant; and polyalkyl methacrylate in an amount of about 3 to 5 wt % as the viscosity modifier.

In particular, the manual transmission oil composition according to the present invention may have a low viscosity as compared to conventional manual transmission oils, and have improved endurance of a transmission, reduced a Rattle noise, and improved fuel efficiency of vehicles by about 1 to 2%.

Further provided are vehicles such as automobiles that comprises a manual transmission oil composition as disclosed herein. Other aspects and preferred embodiments of the invention are discussed infra.

DETAILED DESCRIPTION

It is understood that the term “vehicle” or “vehicular” or other similar term as used herein is inclusive of motor vehicles in general such as passenger automobiles including sport utility vehicles (SUV), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft, and the like, and includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g. fuels derived from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle that has two or more sources of power, for example both gasoline-powered and electric-powered vehicles.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

Unless specifically stated or obvious from context, as used herein, the term “about” is understood as within a range of normal tolerance in the art, for example within 2 standard deviations of the mean. “About” can be understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless otherwise clear from the context, all numerical values provided herein are modified by the term “about”.

Hereinafter reference will now be made in detail to various exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings and described below. While the invention will be described in conjunction with exemplary embodiments, it will be understood that present description is not intended to limit the invention to those exemplary embodiments. On the contrary, the invention is intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims.

Hereinafter, an exemplary embodiment of the present invention will be described in detail.

The present invention provides a manual transmission oil composition which may include: a polyalphaolefin (PAO) synthetic base oil in an amount of about 75 to 85 wt %; an ester-based viscosity modifier in an amount of about 3 to 10 wt %; and an additive in an amount of about 8 to 15 wt % including one or more selected from an anti-wear agent, a detergent dispersant, a friction modifier, an extreme pressure additive and an anti-oxidant.

The polyalphaolefin (PAO) synthetic base oil, as used herein, may be a base oil. In particular, the polyalphaolefin (PAO) synthetic base oil may have an average kinematic viscosity of about 3.8 to 4.2 cSt at a temperature of about 100° C., a viscosity index of about 120 or greater, and a pour point of about −60° C. or less. Moreover, the base oil may be produced through a GTL (gas to liquid) process.

When the average kinematic viscosity of the base oil is less than about 3.8 cSt at a temperature of about 100° C., since a vaporization amount is substantial under such elevated temperature condition, an amount of the oil used may increase. Furthermore, when the average kinematic viscosity is greater than about 4.2 cSt, since an increase in viscosity is substantial at low temperatures, a gear-shifting property may be reduced and fuel efficiency may deteriorate at the low temperatures. Accordingly, the base oil having the kinematic viscosity within the aforementioned range may be used. In particular, the base oil may be used in an amount of about 75 to 85 wt % based on the total weight of the manual transmission oil composition.

The ester-based viscosity modifier, as used herein, may be added to improve endurance of the transmission and form an oil film. In particular, the ester-based viscosity modifier may be, but not limited to, a hybrid olefin ester-based copolymer.

The hybrid olefin ester-based copolymer as used herein may have a backbone including units derived from a C6 or greater α-olefin monomer and an ethylenically unsaturated carboxylic acid or derivatives thereof, and, the backbone may further include a vinyl aromatic compound monomer. In particular, a mole ratio between the C6 or more α-olefin monomer and the ethylenically unsaturated carboxylic acid or derivatives thereof may be of about 1:3 to 3:1. Further, the copolymer may selectively include a nitrogen functional group. Moreover, an ester functional group of the copolymer may be derived from an alcohol mixture as described in International Publication No. WO2013-123160, which is incorporated herein by reference in its entirety. It is also appreciated that MERIDIAN™ from Lubrizol Corp may provide a suitable option for a representative viscosity modifier. In the related arts, however, the hybrid olefin ester-based polymer has not yet used or added to the manual transmission oil to improve endurance of the transmission.

The ester-based viscosity modifier may be used in an amount of about 3 to 10 wt % based on the total weight of the manual transmission oil composition or particularly in an amount of about 6.5 to 8.0 wt %. When the amount of the ester-based viscosity modifier is less than about 3 wt %, performance of preventing wear of the transmission may be reduced, and when the amount is greater than about 10 wt %, since the viscosity at elevated temperatures may substantially increase, fuel efficiency of vehicles may deteriorate. Accordingly, the ester-based viscosity modifier may be in an amount of about 3 to 10 wt %.

The additive, as used herein, may include one or more selected from the anti-wear agent, the detergent dispersant, the friction modifier, the extreme pressure additive, and the anti-oxidant. The anti-wear agent may prevent wear between metals and in particular, zinc dithiophosphate may be used as the anti-wear agent, without limitation. The detergent dispersant may be a metal system and disperse sludge, wear debris, and the like generated in the transmission and thus reduce damage in lubrication of parts. In particular, a bissuccinimide type ashless dispersant may be used as the detergent dispersant, without limitation. The friction modifier may maintain a static friction coefficient and a kinetic friction coefficient so as to gear a synchronizer ring without a crash. In particular, an ester phosphate-based compound may be used as the friction modifier. The extreme pressure additive may prevent fusion and wear of parts under a high load and a polysulfide-based compound may be used as the extreme pressure additive, without limitation. The anti-oxidant may prevent gelation by oxidation of the oil and in particular, calcium sulfonate may be used as the anti-oxidant, without limitation. The additive which may has been generally be used in the art may be further included, and may not be limited to the aforementioned examples.

The additive may be used in an amount of about 8 to 15 wt % based on the total weight of the manual transmission oil composition. When the amount of the additive is less than about 8 wt %, basic performance required as the transmission oil such as endurance, a synchronizer ring friction property, and wear prevention performance may be reduced thereby causing trouble in the transmission. When the amount is greater than about 15 wt %, corrosion of copper-based synchronizer ring parts may be promoted. Accordingly, the additive may be used in an amount of about 8 to 15 wt %.

Moreover, the manual transmission oil composition may further include polyalkyl methacrylate in an amount of about 3 to 5 wt % as the viscosity modifier based on the total weight of the manual transmission oil composition.

In particular, the polyalkyl methacrylate viscosity modifier may have a number average molecular weight of about 300,000 to 400,000 and about four to six C₁₂ to C₁₅ polymer chains. The polyalkyl methacrylate viscosity modifier may suppress an increase in viscosity at low temperatures. In addition, the polyalkyl methacrylate viscosity modifier may be used in an amount of about 3 to 5 wt % based on the total weight of the manual transmission oil composition. when the amount of polyalkyl methacrylate is less than about 3 wt %, the viscosity may not appropriately increase at room temperature and elevated temperatures and an excessive increase in viscosity may be caused at low temperatures. When the amount is greater than about 5 wt %, the viscosity may increase at both high and low temperatures and a reduction of the viscosity due to shearing may be caused during an endurance test thereby reducing endurance. Accordingly, the polyalkyl methacrylate may be used in an amount of about 3 to 5 wt % as described above.

The manual transmission oil formed of the resin composition according to various exemplary embodiments of the present invention may have an average kinematic viscosity of about 5 to 6 cSt at a temperature of about 100° C., the average kinematic viscosity of 24 to 30 cSt at a temperature of about 40° C., and the average absolute viscosity of about 4,000 to 10,000 cP at a temperature of about −40° C. Moreover, the manual transmission oil may have the reduced viscosity as compared to conventional manual transmission oils of which an average kinematic viscosity is of about 7 to 15 cSt at a temperature of about 100° C., an average kinematic viscosity is of about 45 to 100 cSt at a temperature of about 40° C., an average absolute viscosity of about 10,000 to 100,000 at a temperature of about −40° C., and gear endurance is of about 40 to 60 hr. In particular, the manual transmission oil of the present invention may secure endurance such as target gear endurance of about 80 to 200 hr of the transmission and improve fuel efficiency of vehicles by 1 to 2%.

Examples

The following examples illustrate the invention and are not intended to limit the same.

Hereinafter, the present invention will be described in more detail through Examples. However, the Examples are set forth to illustrate the present invention, but the scope of the present invention is not limited thereto.

Examples 1 to 3 and Comparative Examples 1 to 4

The manual transmission oils of Examples 1 to 3 and Comparative Examples 1 to 4 were manufactured according to the composition and the content described in Table 1.

TABLE 1 Compositions and contents (unit: wt %) Example Comparative Example Classification 1 2 3 1 2 3 4 Compo- Base oil¹⁾ 84 83 80 87 75 75 75 sition (wt %) Polyalkyl 3 — — 3 — 8 3 methacrylate viscosity modifier²⁾ (wt %) Ester-based 3 7 10 — 15 7 12 viscosity modifier³⁾ (wt %) Additive 10 10 10 10 10 10 10 package⁴⁾ (wt %) Total content (wt %) 100 100 100 100 100 100 100 ¹⁾Eneos PAO4 (kinematic viscosity at a temperature of about 100° C.: about 3.9 cSt; viscosity index: 130; pour point: −69° C.) ²⁾87725 manufactured from Lubrizol Corp. ³⁾MERIDIAN ™ manufactured from Lubrizol Corp. ⁴⁾Anglamol 2141 manufactured from Lubrizol Corp. which includes an anti-wear agent, a detergent dispersant, a friction modifier, an extreme pressure additive, and an anti-oxidant

Test Example Measurement of Physical Properties

Physical properties of the manual transmission oils manufactured according to Examples 1 to 3 and Comparative Examples 1 to 4 were measured by the following method, and the physical property values are described in Table 2.

-   -   (1) Measurement method of the kinematic viscosity: The kinematic         viscosity was measured by using standard ASTM D 445 measurement         method.

(2) Measurement method of the low temperature viscosity: The low temperature viscosity was measured by using standard ASTM D 2983 measurement method.

(3) FZG gear endurance test: FZG gear endurance was measured by using standard FVA No. 2/IV measurement method.

(4) Differential endurance test: Endurance of the differential gear and the ring gear were evaluated by applying the real-vehicle load having the level of about 300,000 km under the driving condition where the differential gear was operated.

(5) Power train endurance test: The actual engine and transmission were equipped to apply the load to each gear-shifting stage under the real-vehicle driving condition of the level of about 300,000 km and thus evaluate endurance.

(6) Constant speed endurance test: The fixed speed and torque were given for each stage by using the motor dynamometer to evaluate endurance.

(7) Measurement method of transferring efficiency (%) of the transmission: The ratio of power inputted into the transmission and power outputted from the transmission were measured.

TABLE 2 Measurement result of physical properties Target Example Comparative Example Classification Unit value 1 2 3 1 2 3 4 Test Kinematic 100° C. cSt 5.3 to 6.0 5.3 5.4 6.0 5.3 11.5 13.2 12.8 result viscosity  40° C. cSt 23 to 30 23 25 30 23 49 59 62 Low −40° C. cP 4000 to 10000 4,000 5,000 10,000 4,000 13,000 25,000 30,000 temperature viscosity FZG gear endurance hr 90 to 200 90 120 200 50 140 140 180 Transmission Differential — There are no OK OK OK NG OK OK OK endurance pitting and Power train — abnormal wear OK OK OK OK OK OK OK endurance in parts such Constant — as gears and OK OK OK NG OK OK OK speed bearings (OK) endurance Transferring % 96 or more 97 97 96 97 95 94 93 efficiency

As described in Table 2, the manual transmission oil compositions of Examples 1 to 3 had the average kinematic viscosity of about 5 to 6 cSt at a temperature of about 100° C., the average kinematic viscosity of about 24 to 30 cSt at a temperature of about 40° C., and the average absolute viscosity of about 4,000 to 10,000 cP at a temperature of about −40° C. In addition, the manual transmission oil compositions of Examples 1 to 3 had the substantially reduced viscosity as compared to Comparative Examples while exhibiting improved results of pitting endurance of about 90 hr or greater as the FZG gear endurance test result. Moreover, the manual transmission oil compositions of Examples 1 to 3 had transferring efficiency of the transmission maintained at about 96% or greater and no abnormality was detected in the endurance test.

According to various exemplary embodiments of the present invention, the manual transmission oil compositions, for example, Examples 1 to 3, may have substantially reduced viscosity and have improved endurance of the transmission. Also, effectiveness of fuel efficiency was enhanced by about 1 to 2% due to the manual transmission oil compositions.

Accordingly, the manual transmission oil composition of the present invention may be advantageous by reducing the viscosity, and further by improving wear resistance of the transmission, and an oil film formed therein may be enlarged to improve gear pitting/scoring and enhance fuel efficiency.

The invention has been described in detail with reference to exemplary embodiments thereof. However, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents. 

What is claimed is:
 1. A manual transmission oil composition comprising: a polyalphaolefin (PAO) synthetic base oil in an amount of about 75 to 85 wt % based on the total weight of the manual transmission oil composition; an ester-based viscosity modifier in an amount of about 3 to 10 wt % based on the total weight of the manual transmission oil composition; and an additive in an amount of about 8 to 15 wt % based on the total weight of the manual transmission oil composition, wherein the additive comprises one or more selected from an anti-wear agent, a detergent dispersant, a friction modifier, an extreme pressure additive, and an anti-oxidant.
 2. The manual transmission oil composition of claim 1, wherein the ester-based viscosity modifier is a hybrid olefin ester-based copolymer having a backbone including units derived from a C₆ or more α-olefin monomer and an ethylenically unsaturated carboxylic acid or derivatives thereof.
 3. The manual transmission oil composition of claim 1, wherein the manual transmission oil composition further comprises polyalkyl methacrylate in an amount of about 3 to 5 wt % as the viscosity modifier.
 4. The manual transmission oil composition of claim 3, wherein the polyalkyl methacrylate has a number average molecular weight of about 300,000 to 400,000 and about four to six C₁₂ to C₁₅ polymer chains.
 5. A manual transmission oil of claim 1, wherein the manual transmission oil has an average kinematic viscosity of about 5 to 6 cSt at a temperature of about 100° C., an average kinematic viscosity of about 24 to 30 cSt at a temperature of about 40° C., and an average absolute viscosity of about 4,000 to 10,000 cP at a temperature of about −40° C.
 6. A manual transmission oil of claim 1 which consists essentially of the polyalphaolefin (PAO) synthetic base oil; ester-based viscosity modifier; and additive.
 7. A manual transmission oil of claim 1 which consists of the polyalphaolefin (PAO) synthetic base oil; ester-based viscosity modifier; and additive.
 8. A vehicle that comprises a manual transmission oil of claim
 1. 